It has been a long standing practice to route the exhaust gasses from the exhaust manifold of an engine or power plant through a muffler and tail pipe, to reduce engine noise. While this is effective for conventional use, the back pressure caused by the exhaust gasses passing through the muffler results in a loss of efficiency which adversely affects the engine performance. Many high performance engines operate most efficiently when the muffler and tail pipe are removed or bypassed. While this improves engine performance, the resulting noise from the engine would prohibit use of the vehicle where unrestricted engine noise would be undesirable.
Therefore, what is needed is a way to selectively route exhaust gasses from the exhaust manifold through a conventional muffler and tail pipe for conventional engine use, while allowing the exhaust gasses to bypass the muffler and tail pipe when peak engine performance is desired, such as during competition racing on land, water, or in the air.
In addition, other types of engines, such as used on farm tractors, combines, or the like, often work best at peak performance when the exhaust gasses are not restricted by a muffler or tail pipe. However, at times it may be desirable to selectively pass exhaust gasses through a muffler and tail pipe in areas where the additional engine noise would be undesirable.